So I was pondering life, laying in bed, and had a sudden revelation. According to the wiki

1939 - World War II begins. Though he wanted desperately to fight in World War II, the Soldier was rejected from every branch of the U.S. military. Undaunted, he bought his own ticket to Europe. After arriving and finally locating Poland, the Soldier taught himself how to load and fire a variety of weapons before embarking on a Nazi killing spree for which he was awarded several medals that he designed and made himself.1949 - The Soldier ends his Nazi killing spree in Poland upon hearing that World War II had already ended in 1945

Enter 1968 when TF2 begins. This leaves 19 years where the Soldier has been missing. Now comes my theory, the soldier has Psychogenic amnesia. This amnesia is triggered by sever stress, not physical or psychological pain, and is common in soldiers who have experienced combat. Now consider that Soldier had no formal training, went on a mass murdering spree, and was running basically on adrenaline. This alone would be enough for a normal man to snap, but he was alone during the whole thing. His amnesia went on to make him forget everything, including his name, except why he was fighting and his weapon training. This would also show why he has a distrusts of different nationality's, he only knows America is good in his eyes. He would later get psychiatric, however because he did not know his name he became Mister Jane Doe. And because he did not remember how to act normally he followed the most American stereotype, a gun toting, eagle loving, screaming, explosion in the background, ready to die for his country soldier.

I do hope you guys like this theory and I would love your thoughts on it. Also I have a Heavy theory in the works about why he likes his guns so much that he would name them and get defensive over them.

Animus wrote:he kills a celebrity (I think an American Celebrity, but I forget.) and lives with Merasmus. Also picked up a Russian Girlfriend. :d

He killed the celebrity because he was Merasmus's roommate and according to him that gives him full right to do that, and he appreciate the Russians after seeing ghost telling him to eat their food, both showing signs of insanity.